Black Lady is a combination of Chibiusa's worst traits, personal fears and insecurities. While she is fueled by the power of the Dark Crystal and Wiseman, she driven by the anger she feels toward her mother and father. Wiseman used memories Chibiusa considered the worst moments of her life and manipulated to a point that suited his purposes.

Otaku Trivia:

1) The TokyoPop version of the manga used both "Black Lady" and "Wicked Lady" for the character's name.

2) Originally, Naoko Takeuchi struggled with a name for Black Lady, initially calling her "the Black Queen", and retaining her childlike appearance.

3) While she makes her only appearance in the second arc of the manga, she is mentioned again in Act 40 after Chibiusa's age is switched with Usagi's due to PallaPalla's magic, causing the Inner Senshi to briefly mistake Chibiusa for Black Lady.